For the problem that laser pulse correlation detector faces challenges of both imperfect narrow-band filter and dependency of background light interference received by parallel detectors, an improved method is proposed. Two of four parallel detectors are used for receiving target signal and background light, while the other two receive background light only. The correlation background light interference is restrained through subtracting background light from the mixed signal before correlation processing. Simulation results demonstrate that the light out of working spectrum is remarkably resisted, and false-alarm probability caused by background light interference is lower effectively, which prove the method is feasible and effective.